Gas modulation to control edge exclusion in a bevel edge etching plasma chamber

ABSTRACT

The various embodiments provide apparatus and methods of removal of unwanted deposits near the bevel edge of substrates to improve process yield. The embodiments provide apparatus and methods with center and edge gas feeds as additional process knobs for selecting a most suitable bevel edge etching processes to push the edge exclusion zone further outward towards the edge of substrates. Further the embodiments provide apparatus and methods with tuning gas(es) to change the etching profile at the bevel edge and using a combination of center and edge gas feeds to flow process and tuning gases into the chamber. Both the usage of tuning gas and location of gas feed(s) affect the etching characteristics at bevel edge. Total gas flow, gap distance between the gas delivery plate and substrate surface, pressure, and types of process gas(es) are also found to affect bevel edge etching profiles.

CLAIM OF PRIORITY

This application claims priority under 35 USC 120 as acontinuation-in-part of application Ser. No. 11/440,561, filed May 24,2006, now U.S. Pat. No. 7,909,960, which claimed priority under 35 USC120 as a continuation-in-part of application Ser. No. 11/237,327, filedon Sep. 27, 2005 now abandoned.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to U.S. patent application Ser. No.11/758,576, filed on Jun. 5, 2007 now U.S. Pat. No. 7,938,931, entitled“Edge Electrodes with Variable Power,” U.S. patent application Ser. No.11/758,584, filed on Jun. 5, 2007, entitled “Edge Electrodes withDielectric Covers,” U.S. patent application Ser. No. 11/440,561, filedon May 24, 2006, entitled “Apparatus and Methods to Remove Films onBevel Edge and Backside of Wafer,” now U.S. Pat. No. 7,909,960. U.S.patent application Ser. No. 11/355,458, filed on Feb. 15, 2006, entitled“Plasma Processing Reactor with Multiple Capacitive and Inductive PowerSources,” and U.S. patent application Ser. No. 11/363,703, filed on Feb.27, 2006, entitled “Integrated Capacitive and Inductive Power Sourcesfor a Plasma Etching Chamber.” The disclosure of each of theabove-identified related applications is incorporated herein byreference.

FIELD OF INVENTION

The present invention relates in general to substrate manufacturingtechnologies and in particular to apparatus and methods for the removalof deposited films and/or etch byproducts from a bevel edge of asubstrate.

BACKGROUND

In the processing of a substrate, e.g., a semiconductor substrate (orwafer) or a glass panel such as one used in flat panel displaymanufacturing, a plasma is often employed. During substrate processing,the substrate (or wafer) is divided into a plurality of dies, orrectangular areas. Each of the plurality of dies will become anintegrated circuit. The substrate is then processed in a series of stepsin which materials are selectively removed (or etched) and deposited.

Typically, a substrate is coated with a thin film of hardened emulsion(such as a photoresist mask) prior to etching. Areas of the hardenedemulsion are then selectively removed, causing parts of the underlyinglayer to become exposed. The substrate is then placed on a substratesupport structure in a plasma processing chamber. An appropriate set ofplasma gases is then introduced into the chamber and a plasma isgenerated to etch exposed areas of the substrate.

During an etch process, etch byproducts, for example polymers composedof Carbon (C), Oxygen (O), Nitrogen (N), Fluorine (F), etc., are oftenformed on the top and the bottom surfaces near a substrate edge (orbevel edge). Etch plasma density is normally lower near the edge of thesubstrate, which results in accumulation of polymer byproducts on thetop and on the bottom surfaces of the substrate bevel edge.

Typically, there are no dies present near the edge of the substrate, forexample between about 2 mm to about 15 mm from the substrate edge.However, as successive purposely deposited films and byproduct polymerlayers are deposited on the top and bottom surfaces of the bevel edge asa result of several different deposition and etch processes, bonds thatare normally strong and adhesive will eventually weaken duringsubsequent processing steps. The purposely deposited films and polymerlayers formed near the bevel edge would then peel or flake off, oftenonto another substrate during substrate transport. For example,substrates are commonly moved in sets between plasma processing systemsvia substantially clean containers, often called cassettes. As a higherpositioned substrate is repositioned in the container, particles (orflakes) of purposely deposited film and byproducts on the bevel edge mayfall on a lower substrate where dies are present, potentially affectingdevice yield.

Dielectric films, such as SiN and SiO₂, and metal films, such as Al andCu, are examples of films that are purposely deposited on thesubstrates. These films can also be deposited on the bevel edge(including the top and bottom surfaces) and do not get removed duringthe etching process. Similar to etching byproducts, these films at beveledge can accumulate and flake off during subsequent processing steps,thereby impacting device yield.

For advanced technologies, it is desirable to expand the usable areas onthe substrate surface to the edge of the wafer (or substrate). Asmentioned above, there are typically no dies present near the edge ofthe substrate, for example between about 2 mm to about 15 mm from thesubstrate edge, which is also called the “edge exclusion zone.” The edgeexclusion zone is a region, such as between about 2 mm to about 15 mmfrom the substrate edge, at the edge of the substrate that is not usableand does not have dies. For advanced technologies, the target is to haveusable area expended to less than about 2 mm from the edge of thesubstrate to increase usable area on the substrate. Therefore, the edgeexclusion zone is targeted to be less than 2 mm.

In view of the foregoing, there is a need for apparatus and methods thatremove unwanted deposits on the bevel edge of the substrates to reducethe edge exclusion zone to be less than 2 mm from the edge ofsubstrates. Such apparatus and methods would expand the usable area andimprove the process yield on the substrate.

SUMMARY

The various embodiments provide apparatus and methods of removal ofunwanted deposits near the bevel edge of the substrates to improveprocess yield. The embodiments provide apparatus and methods with centerand edge gas feeds as additional process knobs for selecting a mostsuitable bevel edge etching process to push the edge exclusion zonefurther outward towards the edge of the substrates. Further theembodiments provide apparatus and methods with tuning gas(es) to changethe etching profile at the bevel edge using a combination of center andedge gas feeds to a flow process and tuning gases into the chamber. Boththe usage of tuning gas and the location of gas feed(s) affect theetching characteristics at the bevel edge. The total gas flow, the gapdistance between the gas delivery plate and the substrate surface,pressure, and the types of process gas(es) are also found to affect thebevel edge etching profiles.

It should be appreciated that the present invention can be implementedin numerous ways, including as a process, an apparatus, or a system.Several inventive embodiments of the present invention are describedbelow.

In one embodiment, a plasma etching processing chamber configured toetch a thin film on a bevel edge of a substrate is provided. The plasmaetching processing chamber includes a bottom edge electrode surroundinga substrate support in the plasma processing chamber. The substratesupport is configured to receive the substrate and the bottom edgeelectrode and the substrate support are electrically isolated from eachother by a bottom dielectric ring. The plasma etching processing chamberalso includes a top edge electrode surrounding a gas distribution plateopposing the substrate support. The top edge electrode and the gasdelivery plate are electrically isolated from each other by a topdielectric ring, and the top edge electrode and the bottom edgeelectrode are configured to generate an etching plasma near the beveledge to remove the thin film on the bevel edge of the substrate. Thedistance between the top edge electrode and the bottom edge electrode isless than about 1.5 cm to confine the treatment plasma.

Further, the plasma etching processing chamber includes a center gasfeed which is embedded in the gas delivery plate. The center gas feed isconfigured to deliver either an etching process gas or a tuning gas intothe plasma processing chamber through the center gas feed. In addition,the plasma etching processing chamber includes a center gas selectioncontroller coupled to a center gas manifold. The center gas manifold iscoupled to a plurality of etching processes and tuning gases. The centergas selection controller is coupled to the center gas feed and selectsthe etching process gas or the tuning gas delivered into the plasmaprocessing chamber. Additionally, the plasma etching processing chamberincludes an edge gas feed configured to deliver either the etchingprocess gas or the tuning gas toward the bevel edge of the substrate,wherein the edge gas feed is disposed above the substrate. Further, theplasma etching processing chamber includes an edge gas selectioncontroller coupled to an edge gas manifold, the edge gas manifold iscoupled to the plurality of etching process and tuning gases. The edgegas selection controller is coupled to an edge gas feed and selects theetching process gas or the tuning gas delivered into the plasmaprocessing chamber through the edge gas feed.

In another embodiment, a method of etching a thin film on a bevel edgeof a substrate in a plasma etching chamber is provided. The methodincludes placing the substrate on a substrate support in the plasmaetching chamber. The method also includes flowing of an etching processgas through a center gas feed or an edge gas feed. The center gas feedand the edge gas feed are disposed above the substrate support. Themethod further includes flowing of a tuning process gas through thecenter gas feed or the edge gas feed. The tuning gas is used to changethe etching plasma characteristics at the bevel edge.

In addition, the method includes generating an etching plasma near thebevel edge of the substrate to etch the thin film on the bevel edge bypowering a bottom edge electrode or a top edge electrode with an RFpower source and grounding the edge electrode that is not powered by theRF power source. The bottom edge electrode surrounds the substratesupport and the top edge electrode surrounds the gas distribution plate,wherein the distance between the top edge electrode and the bottom edgeelectrode is less than about 1.5 cm to confine the treatment plasma.Additionally, the method includes etching the thin film by the generatedetching plasma.

Other aspects and advantages of the invention will become apparent fromthe following detailed description, taken in conjunction with theaccompanying drawings, illustrating by way of example the principles ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be readily understood by the followingdetailed description in conjunction with the accompanying drawings, andlike reference numerals to designate like structural elements.

FIG. 1A shows a cross-sectional view of a thin film near a bevel etch,in accordance with one embodiment of the present invention

FIG. 1B shows a cross-sectional view of a thin film with the film on thebevel edge being removed, in accordance with one embodiment of thepresent invention.

FIG. 1C shows four different bevel edge etching profiles, in accordancewith one embodiment of the present invention.

FIG. 2 shows a cross-sectional view of a plasma system configured togenerate a bevel edge etching plasma, in accordance with one embodimentof the present invention.

FIG. 2A shows a cross-sectional view of center feeds, in accordance withone embodiment of the present invention.

FIG. 2B shows a cross-sectional view of a center feed with multiple gassources, in accordance with one embodiment of the present invention.

FIG. 2C shows a cross-sectional view of edge feeds, in accordance withone embodiment of the present invention.

FIG. 2D shows a cross-sectional view of an edge feed with multiple gassources, in accordance with one embodiment of the present invention.

FIG. 2E shows a cross-sectional view of an enlarged region M with beveledge of FIG. 2, in accordance with one embodiment of the presentinvention.

FIG. 2F shows a cross-sectional view of a plasma system configured togenerate a bevel edge etching plasma, in accordance with anotherembodiment of the present invention.

FIG. 2G shows a top view of a top chamber assembly of the plasma systemof FIG. 2, in accordance with an embodiment of the present invention.

FIG. 2H shows an enlarged diagram of a region around a center gas feed,in accordance with an embodiment of the present invention.

FIG. 2I shows an enlarged diagram of a region around an edge gas feed,in accordance with an embodiment of the present invention.

FIG. 2J shows a top view of a top chamber assembly of the plasma systemof FIG. 2, in accordance with another embodiment of the presentinvention.

FIG. 3A shows bevel etching profiles of 4 different etching processes,in accordance with one embodiment of the present invention.

FIG. 3B shows bevel etching profiles of 4 different etching processes,in accordance with another embodiment of the present invention.

FIG. 3C shows bevel etching profiles of 3 different etching processes,in accordance with one embodiment of the present invention.

FIG. 3D shows bevel etching profiles of 4 different etching processes,in accordance with another embodiment of the present invention.

FIG. 4 shows a process flow of generating a bevel edge etching plasma,in accordance with one embodiment of the present invention.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Several exemplary embodiments for improved mechanisms to removeundesirable deposits on the bevel edges of wafers to improve processyield are provided. It will be apparent to those skilled in the art thatthe present invention may be practiced without some or all of thespecific details set forth herein.

FIG. 1A shows a cross-sectional view of substrate 105 that has asubstrate body 100 with a front side 110, a backside 120 and an edge 130between the front and backsides, in accordance with one embodiment ofthe present invention. Substrate body 100 could be a wafer without otherfilms and features. Substrate body 100 could also have various films andfeatures from prior processing. In FIG. 1A, there is a thin film layer101 covering the substrate front side 110 and substrate edge 130. Thethin film layer 101 could be a dielectric layer, such as silicon dioxide(SiO2), or silicon nitride (SiN), a metal layer, such as tantalum (Ta),tantalum nitride (TaN), copper (Cu), or Aluminum (Al). Thin film layer101 can be a layer of photoresist or etching byproducts. Further, thethin film layer 101 could also be a dielectric layer or a metal layermixed with photoresist and/or etching byproducts. The thickness of thethin film 101 can range from a few angstroms to a few microns.

The thin film layer 101 extends to a distance Y from the substrate edge130 of the substrate 105. In one embodiment, the distance Y extends allthe way to the center of backside surface 120 of substrate body 100. Inanother embodiment, the distance Y is between about 2 mm to about 15 mmfrom the edge 130. The thin film layer 101 on the bevel edge needs to beremoved to prevent accumulation of thin film that results in possibleflaking during future substrate handling and other substrate processing.As described above, for advanced technologies, the trend is to extendthe usable area to the edge of the substrate. Distance “X” is thedistance from edge 130 that thin film layer 101 should be removed. Foradvanced technologies, distance “X” is less than about 2 mm, preferablyless than about 1 mm, and more preferably less than about 0.5 mm. Thesurface area beyond distance X (towards the center of substrate) isconsidered usable area for constructing devices.

FIG. 1B shows that after the bevel edge etching process, the film on thebevel edge is removed. Thin film layer 101 on the front side is removedto distance “X” from edge 130. As mentioned above, substrate surface 110with thin film layer 101, if not removed during substrate etching inFIG. 1B is considered usable area.

FIG. 1C shows etch rates (ER) near the bevel edge for bevel edge plasmaetching processes. Curves 150, 152, 154, and 156 show three differentetch rate curves near the bevel edge. Curve 150 shows results of aconventional process that produces a broader bevel etch profile near thesubstrate edge. The etch rate is non-zero at a distance greater than 2mm from the edge, such as edge 130 of FIG. 1A. Curve 152 shows resultsof a process that produces a narrower bevel etch profile than curve 150.The etch rate on the substrate surface is zero until about 2 mm from theedge. Curves 154 and 156 are even narrower than curve 152. Etch rate isnon-zero from the edge to about 1 mm from the substrate edge for curve154 and to about 0.5 mm for curve 156. For process technologies thatrequire edge exclusions less than about 2 mm, even to 1 mm or 0.5 mm,processes that can produce etch curves, such as curves 152, 154 and 156,can be used. For the purpose of reducing the edge exclusion zone to lessthan about 2 mm from the edge of the substrate, processes that producecurves 152, 154, and 156 are better than the process that produces curve150.

FIG. 2 shows an embodiment of a bevel edge plasma processing chamber 200for performing plasma etching near the bevel edge of the substrate.Chamber 200 has a substrate support 240 with a substrate 250 on top. Inone embodiment, the substrate support 240 is an electrostatic chuck,which is powered by a RF (radio frequency) power source (not shown). Inanother embodiment, the substrate support 240 is a regular electrode.The substrate support 240 can be DC (direct current) or RF biased.Opposing the substrate support 230 is a gas plate 260 with a center gasfeed 261. The feed point 264 of the center gas feed 261 is near abovethe center of the substrate. The center gas feed 261 is embedded in thegas plate 260 and located near the center of substrate 250. In oneembodiment, there are a number of center gas feeds, such as gas feeds261′, 261″, and 261″, which are coupled to different gas sources, suchas gas source 271″ (for gas X), 271″ (for gas Y), and 271″ (for gas Z),as shown in FIG. 2A. In another embodiment, different gas sources feedinto a single center gas feed 261, as shown in FIG. 2B. The processchamber is also equipped with edge gas feeds 263, which are located nearthe bevel edge of substrate 250. In one embodiment, there are a numberof edge gas feeds, such as gas feeds 263′, 263″, and 263″, at theproximity of a location, which are coupled to different gas sources,such as gas sources 273″ (for gas M), 273″ (for gas N), and 273″ (forgas O), as shown in FIG. 2C. In another embodiment, different gassources feed into a single edge gas feed at 263 a particular edgelocation, as shown in FIG. 2D. More details of the edge gas feeds 263will be provided below.

The substrate support can also be RF powered, biased, or grounded.During etching of substrate 250, chamber 200 can be RF powered togenerate capacitively coupled etch plasma or inductively coupled etchplasma. Substrate 250 has a bevel edge 217 that includes a top and abottom surface of the edge of the substrate, as shown in region F ofFIG. 2 and enlarged region M in FIG. 2E. In FIG. 2E, bevel edge 217 ishighlighted as a bold solid line and curve.

FIG. 2F shows an embodiment of a bevel edge etching process chamber 250.The process chamber 250 has a center feed 261 _(P) for process gas, anda center feed 261 _(T) for tuning gas. Both center gas feeds 261 _(P),261 _(T) are coupled to a center gas select 275 _(C), which is coupledto a center gas manifold 276 _(C). The center gas manifold 276 _(C) iscoupled to a number of gas tanks that supplied various process gases andtuning gas(es) (not shown). Alternatively, there could be more than onecenter gas feeds 261P for process gases and more one center gas feeds261T for tuning gases, as described above in FIGS. 2A and 2C. Processchamber 250 also has a number of edge feeds 263 _(P) for processing gas,and a number of edge feeds 263 _(T) for tuning gas. All edge gas feeds261 _(P), 261 _(T) are coupled to edge gas select 275 _(E), which iscoupled to an edge gas manifold 276 _(E). Center gas manifold 276 _(E)is coupled to a number of gas tanks that supply various processing gasesand tuning gas(es) (not shown). Center gas select 275 _(C) receivesinstructions from a chamber process controller 277 and chooses whetherand which gas(es) goes into the center gas feeds, 261 _(P), 261 _(T).Similarly, the edge gas select 275 _(E) receives instructions from achamber process controller 277 and chooses whether and which gas(es)goes into the edge gas feeds, 263 _(P), 263 _(T). The chamber processcontroller 277 is also coupled to other parts of process chamber 250 tocontroller other process parameters, such as temperature, pressure andmovement of the substrate support 240. In one embodiment, the chamberprocess controller 277 is coupled to a processor 278, which is coupledto a key board 280 and a monitor 279. Operators of the processing system250 can enter instruction through the keyboard 280 and the instructionand process condition can be displayed in the monitor 279.

FIG. 2G shows an embodiment of a top view of the chamber top assembly280 of FIG. 2. The top assembly 280 includes chamber top wall 285 (notshown in FIG. 2G) and a gas delivery plate 260, a top dielectric ring211, a top edge electrode, and a top insulating ring 215. The gasdelivery plate 260, the top dielectric ring 211, the top edge electrode,and the top insulating ring 215 are coupled to the top chamber wall 285.The center gas feed 281 is embedded in the gas delivery plate 260. Inthe embodiment shown in FIG. 2G, there are 8 locations of edge gas feeds263, which are disposed between the top dielectric ring 211 and the topedge electrode 210. The 8 locations are evenly distributed around thediameters of the top dielectric ring 211. The 8 locations are merelyused as examples. Other number of locations, such as 4-56 locations, canbe used too.

FIG. 2H shows an embodiment of an enlarged diagram of a region 281around the center gas feed 261 of FIG. 2G. The embodiment shown in FIG.2H illustrates that there could be more than one center gas feeds. Anyreasonable and needed number of center gas feeds is allowed. FIG. 2Ishows an embodiment of an enlarged diagram of a region 283 around theedge gas feed 263 of FIG. 2G. The embodiment shown in FIG. 2Iillustrates that there could be more than one edge gas feeds at eachedge location. Any reasonable and needed number of edge gas feeds ateach edge location is allowed.

FIG. 2 J shows another embodiment of edge gas feed 263 of FIG. 2. Inthis embodiment, edge gas feed 263′ is a gas ring between the topdielectric ring 211 and the top edge electrode 210. Processing gas(es)and/or tuning gas(es) can be delivered evenly to the process chamberthrough the gas ring 263′.

Surrounding the edge of substrate support 240, there is a bottom edgeelectrode 220, made of conductive materials, such as aluminum (Al).Between the substrate support 240 and the bottom edge electrode 220,there is a bottom dielectric ring 221 electrically separating thesubstrate support 240 and the bottom edge electrode 220. In oneembodiment, substrate 250 is not in contact with the bottom edgeelectrode 220. Beyond the bottom edge electrode 220, there is anotherbottom insulating ring 225, which extends the surface of the bottom edgeelectrode 220 facing substrate 250.

Surrounding the gas plate 260, there is a top edge electrode 210, madeof conductive materials, such as aluminum (Al). The top edge electrode210 is electrically insulated from the gas plate 260 by a top dielectricring 211. As mentioned above, the edge gas feed(s) 263 provides processgas(s) to the bevel edge 217 of substrate 250. In one embodiment, theedge gas feeds 263 provide process gas(s) to feeding points 262 facingthe bevel edge 217 of substrate 260 and are between the top edgeelectrode 210 and the top dielectric ring 211. Beyond the top edgeelectrode 210, there is top insulating ring 215, which extends thesurface of the top edge electrode 210 facing substrate 250.

In one embodiment, the bottom edge electrode 220 is coupled to an RFpower source 223 and the top edge electrode 210 is grounded. During asubstrate bevel edge treatment process, the RF power source 223 suppliesRF power at a frequency between about 2 MHz to about 60 MHz and a powerbetween about 100 watts to about 2000 watts to generate a treatmentplasma. During bevel edge treatment the substrate support 240 and thegas delivery plate 260 are kept electrically floating. In anotherembodiment, the bottom electrode 240 is coupled to an RF power source224. During a substrate bevel edge treatment process, the RF powersource 224 supplies RF power at a frequency between about 2 MHz to about60 MHz and a power between about 100 watts to about 2000 watts togenerate a treatment plasma. During bevel edge treatment the gasdelivery plate 3=260 is kept electrically floating, and both the bottomedge electrode 220 and the top edge electrode 210 are grounded.

The two embodiments of hardware configurations described above aremerely examples, other configurations of bevel edge reactors can also beused. For details of other types of bevel edge reactors, see U.S. patentapplication Ser. No. 11/758,576, filed on Jun. 5, 2007, entitled “EdgeElectrodes with Variable Power,” U.S. patent application Ser. No.11/758,584, filed on Jun. 5, 2007, entitled “Edge Electrodes withDielectric Covers,” U.S. patent application Ser. No. 11/440,561, filedon May 24, 2006, entitled “Apparatus and Methods to Remove Films onBevel Edge and Backside of Wafer,” U.S. patent application Ser. No.11/355,458, filed on Feb. 15, 2006, entitled “Plasma Processing Reactorwith Multiple Capacitive and Inductive Power Sources,” and U.S. patentapplication Ser. No. 11/363,703, filed on Feb. 27, 2006, entitled“Integrated Capacitive and Inductive Power Sources for a Plasma EtchingChamber.” The disclosure of each of the above-identified relatedapplications is incorporated herein by reference.

In one embodiment, the space between the top edge electrode 210 and thebottom edge electrode 220, D_(EE), is less than 1.5 cm to ensure theplasma is confined. A D_(EE) of less than 1.5 cm allows the ratiobetween the width (D_(W)) and gap (D_(EE)) of the opening near substrateedge to be less than 4:1, which ensures plasma confinement. D_(W) is thewidth of the opening near the substrate edge. In one embodiment, D_(W)is the width of the bottom insulating ring 225 or the width of the topinsulating ring 215. The chamber pressure is kept between about 20 mTorrto about 100 Torr, and preferably between about 100 mTorr to about 2Torr, during the bevel edge etching process. The spacing between the gasdistribution plate 260 and substrate 250, D_(s), is less than 0.6 mm toensure no plasma is formed between the top electrode 260 and thesubstrate 250 during the bevel edge etching process.

The embodiment of plasma chamber 200 shown in FIG. 2 is merely anexample. Other embodiments of plasma chamber for bevel edge etching arealso possible. In another embodiment, the RF power supply can be coupledto the top edge electrode 210, while the bottom edge electrode 220 isgrounded to generate the capacitively coupled etching plasma.Alternatively, either the top edge electrode 210 or the bottom edgeelectrode 220 can be replaced with an inductive coil buried in adielectric material. In this embodiment, the inductive coil is coupledto a RF power source and the opposing edge electrode is grounded. The RFpower source supplies power to generate an inductively coupled etchingplasma to treat the bevel edge 217. For further description of the beveledge plasma etching chamber see U.S. patent application Ser. No.(11/3440,561), filed on May 24, 2006, entitled “Apparatus and Methods toRemove Films on the Bevel Edge and Backside of Wafer.” The disclosure ofthe above-identified related applications is incorporated herein byreference.

Various experiments have been conducted to study the effects of locationof gas feed(s), total gas flow, tuning gas type, tuning gas flow, thegap distance between the gas plate 260 and substrate 250 on the etchrate profiles at the bevel edge. An exemplary reference process foretching dielectric film is used for these studies. The process (etching)gases include NF₃ and CO₂. The film etched is silicon oxide film (SiO₂)deposited from tetra-ethyl-ortho-silicate (TEOS). The tuning gas, whichis not a reactive gas, used in the study includes nitrogen (N₂), argon(Ar), and helium (He). However, in addition to the above-mentionedtuning gas, other types of non-reactive gas, such as other inert gases,can also be used as tuning gas.

The exemplary reference process with 10 sccm NF₃ and 200 CO₂ fed fromthe center gas feed 261 similar to the center gas feed shown in FIG. 2.The pressure is about 1500 mTorr. The gap distance between the gasdelivery plate 260 and the surface of substrate 250 is about 0.4 mm.

FIG. 3A shows a plot of normalized etch rates on different locations onthe substrate surface near the bevel edge. The normalized etch rates areplotted with the distance from the center of the substrate. The etchrates are normalized to the etch rate at 149.4 mm from the center of thesubstrate. The substrate has a diameter of 300 mm and a radius of 150mm. There are four curves in FIG. 3A. Curve 301 shows the results of thereference process with 10 sccm NF₃ and 200 sccm CO₂ fed from center gasfeed(s). Data for curve 302 are generated using a process similar to theprocess of curve 301, but with the CO₂ gas flow increased from 200 sccmto 500 sccm. Comparing curves 301 and 302, the results show thatincreasing the CO₂ gas flow pushes the etch rate curve toward the beveledge. 500 sccm CO₂ gas extends the area with zero etch rate to about 2.5mm from the edge of substrate. In contrast, when CO₂ gas is at 200 sccm,the etch rate is not zero even when the distance is at about 2.5 mm fromthe edge of substrate.

Curve 303 shows etching results of a process with 10 sccm NF₃ and 200sccm CO₂ fed from center process gas feed, and with an additional 300sccm N₂ tuning gas (non-reactive gas) fed from the center gas feed.Curve 304 shows etching results of a process with 10 sccm NF₃ and 200sccm CO₂ fed from center process gas feed, and with an additional 500sccm N2 tuning gas (non-reactive gas) fed from the center gas feed.

The results show that both the 300 sccm N₂ tuning gas feed and 500 sccmN2 tuning gas from the center gas feed help to push the bevel edgeetching rate profile further out towards the substrate edge, incomparison to the standard process of curve 301. However, none of theprocesses of curves 301, 302, 303, and 304 generate a bevel edge etchingprofile that has zero etch rate at about 2 mm (or at 148 mm location inthe FIG. 3A plot) from the edge of substrate.

FIG. 3B shows a plot of normalized etch rates of 4 different processeson the substrate surface. Curve 305 shows the reference process with 10sccm NF₃ and 200 CO₂ fed from the center gas feed 261. Curve 305 isidentical to curve 301 of FIG. 3A. Data for curve 306 are generatedusing a process similar to the process of curve 305, with the exceptionthat both the NF₃ gas and CO₂ gas are fed from edge gas feed(s), such asedge gas feed 263. Comparing curves 305 and 306, the results show thatfeeding process gases NF₃ and CO₂ from edge gas feed(s) pushes the etchrate curve toward the bevel edge. Processing gas fed from edge gas feedsextends the area with zero etch rate to about 2 mm from the edge ofsubstrate. In contrast, when the processing gas is fed from the centergas feed, the etch rate is not zero even when the distance is 3 mm fromthe edge of substrate.

Curve 307 uses a process similar with curve 305 (reference process) withprocess gases fed from center gas feed(s), and with an additional 500sccm N₂ tuning gas (non-reactive gas) fed from center gas feed. Curve308 a process similar with curve 306, with process gases fed from edgegas feed(s), and with a 500 sccm N₂ tuning gas (non-reactive gas) fedfrom center gas feed. The results show that the 500 sccm N₂ tuning gasfeed from the center gas feed help to push the edge of zero etch ratefrom 2 mm of curve 306 (process gases fed from edge) to 1.8 mm of curve308 (process gases fed from edge). As shown in FIG. 3B, the 500 sccm N₂tuning gas feed from the center gas feed helps to push the edge of zeroetch rate from greater than 3 mm for curve 305 (process gases fed fromcenter) to 2.6 mm for curve 307 (process gases fed from center). Theresults favor feeding process gases from the edge, in comparison tofeeding process gases from the center. In addition, the results alsoshow that 500 sccm of N₂ turning gas from center gas feed(s) also canpush the boundary of zero etch rate further towards the edge ofsubstrate. Both processes with process gases fed from substrate edge(curves 306 and 308), either with 500 N₂ tuning gas (curve 308) orwithout N₂ tuning gas (curve 306), generate bevel edge etching profilesthat have zero etch rate at about 2 mm or less than 2 mm from the edgeof substrate. Feeding process gases near the bevel edge is crucial inpushing the boundary to zero etch rate to 2 mm from the edge ofsubstrate.

Experiments with varying amount of N₂ tuning gas, 300 sccm, 500 sccm,and 750 sccm, fed from center gas feed(s) show that etch profile atbevel edge for N₂ tuning gas at 500 sccm is slightly better than resultsfor 300 sccm and 750 sccm N2 tuning gas in terms of pushing the etchprofile outward toward the edge. However, the results for 300 sccm and750 sccm N₂ tuning gas processes are not too different from those of 500sccm N₂ tuning gas process.

Experiments with higher CO₂ flow (300 sccm vs. 200 sccm) fed from centerfeed shows that increased CO₂ flow helps push the etch rate profileoutward towards the edge of substrate.

In addition, comparing the results of the reference process to a processwith 20 sccm NF₃ and 400 sccm CO₂ (2× total flow) fed from the centergas feed shows that the increased total flow helps to push the etch rateprofile outward towards the edge of the substrate. For the 2× total flowprocess, the edge of zero etch rate is at about 2.2 mm from the edge ofsubstrate. In contrast, the edge of zero etch rate for the referenceprocess is more than 3 mm from the edge of substrate.

FIG. 3C compares the results of 3 different processes. Curve 309 isgenerated using the process with 10 sccm NF₃ and 200 sccm CO₂ at thesubstrate edge, and with an additional 750 sccm N₂ tuning gas fed fromcenter. The process is run at normal gap space of 0.4 mm The results ofcurve 309 is very close to curve 308 of FIG. 3B. As mentioned above, theresults of using 750 sccm N₂ tuning gas and 500 sccm N₂ gas at centerfeed(s) are quite close. Curve 310 uses the same process as curve 309,with the exception of using a gap space of 0.35 mm between gas deliveryplate and the substrate. Curve 311 uses the same process as curve 309,with the exception of using a gap space of 0.45 mm between gas deliveryplate and the substrate. The results show that a gap space of 0.4 mmyields the best results.

FIG. 3D compares the results of 4 different processes. Curve 312 isgenerated using a process with 10 sccm NF₃ and 200 sccm CO₂ fed at thesubstrate edge. Curve 313 is generated using the same process as curve309, but with an additional 500 sccm N₂ tuning gas fed at the center gasfeed. The results show a similar conclusion, as the previouslymentioned, that adding 500 sccm N₂ tuning gas helps push the edge ofzero etch rate further outward (comparing curves 306 and 308 of FIG.3B). Curve 314 uses the same process as curve 313, but with a differenttuning gas Ar at the same flow rate of 500 sccm. The effect of adding500 sccm Ar tuning gas is worse than adding 500 sccm N₂ tuning gas(curve 313) and is even worse than not adding any tuning gas at all(curve 312). Curve 315 uses a process with 10 sccm NF₃ and 200 sccm CO₂at the substrate edge (similar to curves 312, 313, and 314), but thetuning gas fed at the center gas feed is a combination of 200 sccm N₂with 500 sccm helium (He). The results show that the combination of 200sccm N₂ with 500 sccm He yields best results.

The results above show that having center and edge gas feeds provideadditional process knobs to use for selecting a most suitable bevel edgeetching process. In addition, adding a tuning gas, such as N₂, Ar, orHe, or a mixture of multiple tuning gases can change the etching profileat the bevel edge of the substrate. Further the total gas flow and gapdistance between the gas delivery plate and the substrate surface canalso affect etching profiles. In addition, as shown in the results anddescription above, process gas types can have an impact on the etchingprofiles and interact with the tuning gas. The various factors mentionedabove either change the plasma composition, or changes characteristicsat the bevel edge. The changes affect the bevel edge etching profiles.

FIG. 4 shows an exemplary process flow 400 of generating a bevel edgeetching plasma by feeding process gas from edge gas feed(s) and feedinga tuning gas from center gas feed(s) to a process chamber. At step 401,a substrate is place on a substrate support in a bevel edge etch plasmachamber. At step 402, process gas(es) is fed to either an edge gasfeed(s) or a center gas feed(s) in the processing chamber. At anoptional process step 403, a tuning gas(es) is fed to either an edge gasfeed(s) or a center gas feed(s) in the processing chamber. At step 404,an etching plasma is generated near the bevel edge of the substrate bypowering either a top edge electrode or a bottom edge electrode. If thetop edge electrode is powered, the bottom edge electrode is grounded. Ifthe bottom edge electrode is powered, the top edge electrode isgrounded. At step 405, the thin film at the bevel edge is removed by thebevel edge etching plasma. The plasma etching chamber is configured togenerate the bevel edge etching plasma that etches thin film at thebevel edge with edge exclusion zone less than about 2 mm from the edgeof substrate. In one embodiment, the edge exclusion zone is less thanabout 1 mm from the edge of substrate. In another embodiment, the edgeexclusion zone is less than about 0.5 mm from the edge of substrate.

The exemplary processes discussed above are for TEOS SiO₂ etching.However, the concept of the present invention can be for etching anytypes of films, such as other dielectric films, metal films,semiconductor films, and barrier films, at bevel edges. Tuning gas,location of gas feed(s), gap distance, total gas flow, type ofprocessing gas can all have an impact on the etching profiles at thebevel edge.

Although the foregoing invention has been described in some detail forpurposes of clarity of understanding, it will be apparent that certainchanges and modifications may be practiced within the scope of theappended claims. Accordingly, the present embodiments are to beconsidered as illustrative and not restrictive, and the invention is notto be limited to the details given herein, but may be modified withinthe scope and equivalents of the appended claims.

1. A plasma etching processing chamber configured to etch a thin film ona bevel edge of a substrate, comprising: a bottom edge electrodesurrounding a substrate support in the plasma processing chamber,wherein the substrate support is configured to receive the substrate andthe bottom edge electrode and the substrate support are electricallyisolated from each other by a bottom dielectric ring, the bottomdielectric ring having a raised portion closer to a surface of thesubstrate support and a lowered potion near the bottom edge electrode; atop edge electrode surrounding a gas distribution plate opposing thesubstrate support, wherein the top edge electrode and the gasdistribution plate are electrically isolated from each other by a topdielectric ring, and the top edge electrode and the bottom edgeelectrode are configured to generate an etching plasma near the beveledge to remove the thin film on the bevel edge of the substrate, whereinthe distance between the top edge electrode and the bottom edgeelectrode is less than about 1.5 cm to confine the etching plasma; acenter gas feed embedded in the gas distribution plate, wherein thecenter gas feed is configured to deliver either an etching process gasor a tuning gas into the plasma processing chamber through the centergas feed; a center gas selection controller coupled to a center gasmanifold, and wherein the center gas selection controller is coupled tothe center gas feed and selects the etching process gas or the tuninggas delivery into the plasma processing chamber; an edge gas feedconfigured to deliver either the etching process gas or the tuning gastoward the bevel edge of the substrate, wherein the edge gas feed isdisposed above the substrate; and an edge gas selection controllercoupled to an edge gas manifold, and wherein the edge gas selectioncontroller is coupled to edge gas feed and selects the etching processgas or the tuning gas delivery into the plasma processing chamberthrough the edge gas feed.
 2. The plasma etching processing chamber ofclaim 1, further comprising: a top insulating ring surrounding andcoupled to the top edge electrode, wherein the surface of the topinsulating ring that faces the substrate aligns with the surface of thetop edge electrode that faces the substrate; and a bottom insulatingring surrounding and coupled to the bottom edge electrode, wherein thesurface of the bottom insulating ring that faces the top insulating ringaligns with the surface of the bottom edge electrode that faces the topedge electrode.
 3. The plasma etching processing chamber of claim 2,wherein the top insulating ring and the bottom insulating ring confinethe cleaning plasma generated by the top edge electrode and the bottomedge electrode.
 4. The plasma etching processing chamber of claim 2,wherein the edge gas feed is located between the top dielectric ring andthe top edge electrode.
 5. The plasma etching processing chamber ofclaim 4, wherein there are a plurality of edge gas feeds evenlydistributed around the outer diameter of the top dielectric ring.
 6. Theplasma etching processing chamber of claim 2, wherein a ratio of a widthof the bottom insulating ring to the distance between the top edgeelectrode and the bottom edge electrode is less than about 4:1.
 7. Theplasma etching processing chamber of claim 1, wherein the etchingprocess gas is fed from the edge gas feed and the tuning gas is fed fromthe center gas feed.
 8. The plasma etching processing chamber of claim1, wherein there are more than one center gas feeds and more than oneedge gas feeds.
 9. The plasma etching processing chamber of claim 1,wherein both the center gas manifold and the edge gas manifold arecoupled to a plurality of processing gases.
 10. The plasma etchingprocessing chamber of claim 1, wherein the thin film on the bevel edgebeing etched is selected from a group consisting of a dielectric film, ametal film, a photoresist film, a semiconductor film, and a combinationof the these films.
 11. The plasma etching processing chamber of claim1, wherein thin film is a dielectric film, and the etching process gasincludes an oxygen-containing gas, and a fluorine-containing gas. 12.The plasma etching processing chamber of claim 1, wherein the tuning gasincludes nitrogen or an inert gas.
 13. The plasma etching processingchamber of claim 1, wherein the top edge electrode is coupled to a RFpower source to supply power and the bottom edge electrode is grounded,or the bottom edge electrode is coupled to a RF power source to supplypower and the top edge electrode is grounded to generate the treatmentplasma.
 14. The plasma etching processing chamber of claim 1, whereinthe distance between the gas distribution plate and the surface of thesubstrate facing the gas distribution plate is less than about 0.6 mm.15. The plasma etching processing chamber of claim 1, wherein theetching plasma near the bevel edge has zero etching at greater thanabout 1 mm from an edge of the substrate.
 16. A plasma chamberconfigured to etch a bevel edge of a substrate, comprising: a bottomedge electrode surrounding a substrate support in the plasma chamber,wherein the substrate support is configured to receive the substrate andthe bottom edge electrode and the substrate support are electricallyisolated from each other by a bottom dielectric ring, the bottomdielectric ring having a raised portion closer to a surface of thesubstrate support and a lowered potion near the bottom edge electrode; atop edge electrode surrounding a gas distribution plate opposing thesubstrate support, wherein the top edge electrode and the gasdistribution plate are electrically isolated from each other by a topdielectric ring, and the top edge electrode and the bottom edgeelectrode are configured to generate an etching plasma near the beveledge; a center gas feed embedded in the gas distribution plate, whereinthe center gas feed is configured to deliver a first gas into the plasmachamber through the center gas feed; a center gas selection controllercoupled to a center gas manifold, and wherein the center gas selectioncontroller is coupled to the center gas feed; an edge gas feedconfigured to deliver a second gas into the plasma chamber toward thebottom edge electrode; and an edge gas selection controller coupled toan edge gas manifold, and wherein the edge gas selection controller iscoupled to edge gas feed.
 17. A chamber, comprising: a bottom edgeelectrode surrounding a substrate support in the chamber, wherein thesubstrate support is configured to receive the substrate and the bottomedge electrode and the substrate support are electrically isolated fromeach other by a bottom dielectric ring, the bottom dielectric ringhaving a raised portion closer to a surface of the substrate support anda lowered potion near the bottom edge electrode; a top edge electrodesurrounding a gas distribution plate opposing the substrate support,wherein the top edge electrode and the gas distribution plate areelectrically isolated from each other by a top dielectric ring; a centergas feed embedded in the gas distribution plate, wherein the center gasfeed is configured to direct a first gas into the chamber through thecenter gas feed; an edge gas feed configured to direct a second gas intothe chamber between the top and bottom edge electrodes; and manifoldsfor enabling flow of the first and second gases into the chamber duringprocessing in the chamber.